import java.util.Scanner;

/**
 * @author zhaoqian
 * @create 2021/8/30 13:24
 */
public class String1 {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            String str = in.nextLine();
            System.out.println(test(str));
        }
    }
    public static String test(String str){
        int min=100;
        int [] sum=new int[str.length()];
        for (int i=0;i<str.length();i++){
            char c = str.charAt(i);
            for (int j=str.length()-1;j>=0;j--){
                char c1 = str.charAt(j);
                if (c==c1){
                    sum[i]++;
                }
            }
        }
       for (int i =0 ; i<str.length();i++){
           if (sum[i]<min){
               min=sum[i];
           }
       }
        StringBuilder stringBuilder = new StringBuilder();
       for (int k=0;k<str.length();k++){
           if (sum[k]!=min){
            stringBuilder.append(str.charAt(k));
           }
       }
        return stringBuilder.toString();
    }
}
